Pressure-controlled downhole actuators

A system comprising:

• an actuator mechanism configured for incorporation in a tool to be employed in a downhole drilling environment in which the actuator mechanism is exposed to ambient wellbore fluid, the actuator mechanism comprising a housing and an actuated member that is mounted on the housing and that is configured for hydraulically actuated movement relative to the housing in response to establishment of a flow connection, via an activation conduit defined by the housing, between ambient wellbore fluid and an activation volume defined by the housing, the actuator mechanism is further configured for deactivation, subsequent to switching of the activation closure device to the opened state, in response to establishment of a flow connection between the ambient wellbore fluid and a deactivation volume of the actuator mechanism via a deactivation conduit defined by the actuator mechanism;
• a plurality of different activation closure devices configured for interchangeable, removable and replaceable mounting on the actuator mechanism, each activation closure device being configured for, when mounted on the actuator mechanism, substantially closing off the activation conduit at below-threshold wellbore fluid pressures, and for automatically switching, in response to ambient wellbore fluid pressures greater than a corresponding activation threshold, to an opened state in which the activation volume is in flow connection with ambient wellbore fluid via the activation conduit;
• and
• a plurality of different deactivation closure devices configured for interchangeable, removable and replaceable mounting on the actuator mechanism, each deactivation closure device being configured for, when mounted on the actuator mechanism, substantially closing off the deactivation volume at below deactivation-threshold wellbore fluid pressures, and for automatically switching, in response to ambient wellbore fluid pressures greater than a corresponding deactivation threshold, to an opened state in which the deactivation volume is in flow connection with ambient wellbore fluid via the deactivation conduit.

A method comprising:

• providing an actuator mechanism at a downhole location such that the actuator mechanism is exposed to ambient wellbore fluid, the actuator mechanism comprising
• a housing that defines an activation volume an activation conduit leading into the activation volume, a deactivation volume, and a deactivation conduit leading into the deactivation volume,
• an actuated member mounted on the housing and configured for hydraulically actuated movement relative to the housing in response to flow of wellbore fluid into the activation volume,
• an activation closure device mounted on the housing to isolate the activation volume from the ambient wellbore fluid by closing off the activation conduit, the activation closure device being configured to open the activation conduit in response to wellbore fluid pressures exceeding a predetermined activation threshold level, and
• a deactivation closure device mounted on the housing to isolate the deactivation volume from the ambient wellbore fluid by closing off the deactivation conduit;
• causing wellbore pressure levels at the actuator mechanism exceed the activation threshold level, thereby to cause automatic opening of the activation conduit by the activation closure device, resulting in hydraulically actuation of the actuated member by action of the wellbore fluid;
• and
• causing wellbore pressure levels at the actuator mechanism to exceed a predetermined deactivation threshold level, thereby triggering automatic opening of the deactivation conduit by the deactivation closure device, to cause the activation of the actuator mechanism.